Recently, in applications such as label package doubling as a protection of a glass bottle and a PET bottle etc. and display of articles, cap sealing and accumulation package, there have been widely used drawn films (so-called heat shrinkable films) composed of a polyvinyl chloride resin, a polystyrene resin, a polyethylene resin or the like. Of these heat shrinkable films, a polyvinyl chloride film has problems that heat resistance is low, and it generates hydrogen chloride gas in incineration and causes dioxin. A polystyrene film has problems that it is inferior in chemical resistance, as well as an ink with a special composition needs to be used in printing, it requires high temperature incineration and generates a lot of black smoke accompanied by an abnormal odor. Therefore, as a shrink label, there has been widely used a polyester-based heat shrinkable film which is high in heat resistance, easy to incinerate, and excellent in chemical resistance, and the use amount tends to increase being accompanied by an increase in turn volume of PET containers.
Further, as a heat shrinkable film, a film is generally utilized which greatly shrinks in the width direction in terms of handleability in label production. Hence, the conventional heat shrinkable polyester film has been produced by drawing at a high ratio in the width direction in order to exhibit a sufficient shrinkage force in the width direction at heating.
However, in the summer season, when the temperature is high, if a heat shrinkable polyester film is stored in an outside storehouse where the temperature is not controlled, there is a problem in that the phenomenon of film shrinkage (so-called natural shrinkage) occurs, reducing the product width. In addition, similarly, in the case of storage in a storehouse where the temperature is high, there is a problem in that the shrinkage in the main shrinkage direction decreases, and, when the film is cut into a label and attached on a container or the like by heat shrinkage, it is not possible to perform attachment beautifully and efficiently unless the temperature conditions for heat shrinkage are changed. Therefore, a heat shrinkable polyester film is usually stored under low-temperature conditions at a temperature of 25° C. or less. However, in terms of delivery, cost, and recent environment, storage at a low temperature in the summer season or the like is undesirable.